[Bldg-sim] exhaust air liquid heat recovery loop

[chris.malcolm.yates at gmail.com]

Hi all,

 

I will resist the temptation to say “happy” new year. Perhaps, for 2021, the
expression “moderately relieved” new year is more appropriate (it’s
certainly more British). I hope as many of you as possible have avoided
covid. I know there are some members of this list who have not been so
fortunate. God speed your recovery.

 

In IDA ICE, there is an option to model a liquid heat recovery loop in the
exhaust of an air handling unit (image attached). In essence, this is just
putting a cooling coil in the exhaust. Heating, including heat recovery, is
after all as much a cooling process as it is a heating process. This cooling
coil can then integrate with some form of heat recovery/ reversible chiller
– a bit like a run-a-round coil heat recovery on steroids!

 

This works in theory. However, I was just wondering how prevalent it is in
practice. Would I be naïve to present this as an option to clients? I know
I’ve not come across this in the UK. Is it just a Scandinavian thing?

 

I’d be very grateful to hear of any projects that have successfully (or
unsuccessfully!) integrated heat recovery via exhaust air liquid loops. 

 

It seems to me that the benefits could be manifold:

*	“decoupling”: Heat recovery potential increases as the building gets
warm, but with traditional plate or thermal wheel heat recovery the demand
for it simultaneously decreases. By buffering the heat to water, or
re-directing it elsewhere (e.g. SHW) heat recovery becomes more general
purpose.
*	A useful load for the chiller during periods of low chiller load.
There are well understood problems with chillers cycling on/off during
periods of low load – aka “low delta T syndrowm”. By dual purposing chiller
equipment for heat recovery, it provides a stable baseload for chillers
during these periods.

 

Kind regards

 

Chris

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